Lifting construction for lift truck



Oct. 18, 1960 B. l. ULINSKI LIFTING CONSTRUCTIONFOR LIFT TRUCK 4 Sheets-Sheet '1 Filed March 29, 1956 1 Flank INVENTOR.

6. Z. LL/AJ 06/ BY ATTORNEY Oct. 18, 1960 LIF'TING CONSTRUCTION FOR LIFT TRUCK I iled March 29, 1956 ATTORNEY B. l. ULIA lSKI 2,956,776

4 Sheets-Sheet 2 Oct. 18, 1960 B. l. ULINSKI 2,956,776

LIFTING CONSTRUCTION FOR LIFT TRUCK Filed March 29, 1956 4 Sheets-Sheet :5

INVENTOR. -1- ALA/J1, BY

ATTORNEY Oct. 18, 1960 B. I. ULINSKI 2,956,776

LIFTING CONSTRUCTION FOR LIFT TRUCK Filed March 29, 1956 4 Sheets-Sheet 4 INVENTOR. -6. l? a 04m 16/ ATTOR/Vf) Patented Oct. 18, 1960 LIFTING CONSTRUCTION FOR LIFT TRUCK Bronislaus I. Ulinski, Flossmoor, Ill., assignor to The Yale & Towne Manufacturing Company, Stamford, Conn., a corporation of Connecticut Filed Mar. 29, 1956, Ser. No. 574,703

9 Claims. (Cl. 254-10) This invention relates to industrial trucks and more particularly to an industrial truck of the type having a lifting head and an elevating platform, the lifting head being supported at its forward end by a steering and traction wheel while the elevating platform is supported at its rear end by lifting wheels, and the elevating platform and lifting head mutually supporting one another through parallel links arranged in the form of parallelogram.

Trucks of this class are so constructed that the elevating platform may be raised relatively to the lifting head through swinging movement of the elevating platform on the links relatively to the lifting head, the said links operating in parallelogram fashion to hold the lifting head and the elevating platform in predetermined relation at all times. It is preferred, in trucks of this class, to effect movement of the lifting wheels relatively to the elevating platform so as to raise the rear end of the platform relatively to the ground at the same time that the elevating platform is raised relatively to the lifting head at its opposed end.

It is very important, in trucks of this class, that the overall length of the truck be maintained at a minimum. This means that the parallel links must be mounted so as not to contribute to the over-all length of the truck. It is also important that the lifting means, usually in the form of a hydraulic ram, be so mounted as to be effective and still not contribute to the truck length.

The contribution of this invention relates to the arrangement of the lifting links and the hydraulic ram, and also to the hydraulic ram construction, whereby a truck of the particular class may be operated effectively and without requiring the lengthening of the truck beyond that necessary for the housing of the operating elements of the truck.

As a particular feature of my invention, I utilize a hydraulic ram in which the piston is extended relatively to the cylinder of the ram when the elevating platform is in its lowered position, so that the inward movement of the piston effects the lifting of the elevating platform. As another feature of this part of my invention, the reservoir for the hydraulic ram may be formed as part of the cylinder of the ram and preferably is the cylinder itself. Thus, by so constructing the cylinder that the ram piston when moving inwardly will not move to the end of the cylinder, the space between the end of the piston and the end of the cylinder functions as a reservoir.

A further feature of the invention resides in the utilization of a support sleeve for mounting the hydraulic ram so that it may pivot relatively to the truck as it effects the lifting of the elevating'platform. The sleeve, because of the particular construction of the ram cylinder, occupies part of that space in the cylinder that functions as the reservoir, therefore effectively mounting the ram for movement. In other words, the space in the cylinder between the end of the piston when the piston has lifted the truck and the end of the cylinder, has passing therethrough, a sleeve. The inside of the sleeve is adapted to from the outside as will be apparent from a review of the specification and drawings of this application.

As a still further feature of the invention, I am able through the use of my new hydraulic ram, to obviate the need for equipping the truck with springs to force the elevating platform downwardly to a lowered position when the hydraulic ram is conditioned to allow movement to that position. Thus, as a particular feature of this part of the invention, a spring is placed inside the ram between the piston and the cylinder and operates at all times to move the piston outwardly of the cylinder. Because of that contribution of my invention involving the positioning of the piston outwardly of the cylinder when the elevating platform is fully lowered, I am able to use a very effective compression spring between the cylinder and piston to force the piston outwardly of the cylinder and to elfect the lowering of the elevating platform. This feature alone has very considerable merit, as those skilled in the art will appreciate.

As a still further feature of my invention, the lowering spring is particularly guided by means including the suption of the support sleeve, all as will be set forth below.

As a still further feature of the invention, I employ a very novel and unique arrangement of the parallel lifting links which contribute the parallelogram movement of the elevating platform relatively to the lifting head.

Thus, these parallel links are mounted in very close relation to one another between the lifting head and the elevating platform, with the links in a very low position in the space that is present between the lifting head and 1 the elevating platform in trucks of the particular class. This space, as those skilled in the art will appreciate, is below the battery normally found in trucks of this class, and in horizontal alignment with the wheel that supports the lifting head. It is an important feature of my invention that I am able to utilize this normally present and available space for the purpose of equipping my truck with effective lifting means.

I have thus outlined rather broadly the more important features of my invention in order that the detailed description thereof that follows maybe better understood, and in order that my contribution to the art may be better appreciated. There are, of course, additional features of my invention that will be described hereinafter and which will form the subject of the claims appended here to. Those skilled in the art will appreciate that the conception on which my disclosure is based may readily be utilized as a basis for the designing of other structures for carrying out the several purposes of my invention. It is important, therefore, that the claims be regarded as including such equivalent constructions as do not depart from the spirit and scope of my invention, in order to prevent the appropriation of my invention by those skilled in the art.

In the accompanying drawings, in which I show one preferred embodiment of my invention:

Fig. 1 is a perspective view showing an industrial truck that utilizes my invention;

Fig. 2 is a longitudinal section of my novel lifting ram;

Figure 3 is a cross section on the line 3-3 of Fig. 2;

Fig. 4 is a longitudinal section of the front part of the truck, showing my invention with the platform in its Fig. 4;

support a pivot shaft, the sleeve itself sealing the cylinder Fig. 7 shows the mounting pivot for the ram.

Referring now more particularly to Fig. 1 of the drawings, reference numeral 11 indicates generally a truck of the particular class having a lifting head 12 that carries a battery 13 in a casing 14. i As is usual in trucks of this class, the forward portion of the lifting head 12 is supported on a traction unit 16 that has a traction motor 17, a ground-engaging steering and traction wheel 18 and a casing 19 for gears connecting the motor 17 and the wheel 18. The traction unit 16 is mounted for steering rotation on a vertical axis on the lifting head 12, and is equipped with the usual steering handle 21. For convenience in operation, the steering handle 21 is pivoted at 22 for vertical movement on the traction unit 16, and at its upper end carries suitable control means 23 for the truck.

Extending rearwardly from the lifting head 12 is an elevating platform designated generally by reference numeral 24. Since I have chosen to illustrate a truck of the type that handles pallets, I show the elevating platform 24 constructed with a pair of rearwardly extending legs 26 on the forward part 27 of said elevating platform. At the rear end of each leg 26 are load wheels 28, Figs. 1 and 5, with openings 29 for those wheels in the top walls 31 of said legs.

I effect the raising and lowering of the elevating platform 24 through a novel arrangement utilizing a hydraulic ram, indicated generally by reference numeral 32, and best seen in Figs. 4, 5, and 6. This ram 32 will be fully describedin due course, and I shall merely note here that the ram has a cylinder 33 pivoted at one endto the lifting head 12, and a piston 34 moving in 'said cylinder.

I further utilize in my novel construction a system of links, indicated generally by reference numeral 36, through which ram piston 34 acts to lift the elevating platform 24. Thus, as shownin Figs. 4, and 6, the outward endof piston34 is pivotally attached by means of a pin 37 to a pair of legs 38 that are integral with a rocker shaft 39. It is important to observe that I mount the rocker shaft 39 in a very low position below the battery 13. I prefer to utilize for this purpose a rod 41 that is supported in a transverse position onthe lifting head through brackets 42, Fig. 6. Integral with the rocker shaft 39 is a series of parallel arms 43 which are disposed in pairs at an.

angle to the legs 38, as shownin Figs. 4 and 5. The arms 43 are pivoted through pins 44 to lugs 46 on the elevating platform 24 and can have very considerable swinging movement in a vertical direction despite the position of rocker shaft 39 in the space below the battery. The arms 43 further have extensions 47 whereby to actuate the rear load wheels 28 in a rather usual way. Merely for purposes of disclosure, I show a tension rod 59 pivoted to and also that those arms will move upwardly when the. piston 34 moves inwardly, that is, from the position shown in Fig. 5 to that shown in Fig. 4, thus lifting the elevating platform 24 relatively to the lifting head. On the other hand, movement of thepiston 34 outwardly from the cylinder 33 will efiectlowering of the elevating platform 24. My linkage system 36 has further a pair of upper links 48 which are parallel to the arms 43 and, like the arms 43, are pivoted to, the lifting head 12 in the space below the battery 13. 1 I prefer to utilize for this purpose pivots 49 on bearings 51 atopposite sides of the lifting head 12, as may be seen in Figs. 4, 5 and 6. The upper links 48 are pivoted to the elevating platform 24 through a shaft 52 on which they are held by nuts 54, with the shaft rotating on a bearing tube 53Jon the forward standard 27 of, the platform. The arms 43 and the upper links 48 thereby form a parallelogram arrangement that will hold the elevating platform24 in predetermined relation to the lifting head 12 as the platform is raised and lowered. The corners of this parallelogram, naturally, are represented by pivots 44, 49, shaft 52, and the rod 41.

It is extremely important to realize that the construction I have described enables me to mount the parallelogram links in very close relation to one another. Actually, the links can be quite short, yet. it is possible to effect through those links a large vertical movement of the truck platform. Through my construction, I achieve a very compact arrangement of the links, and I am able moreover. to.

mountthe links in a very low position in the space below the battery. This in turn. enables me to place not only the links but thehydraulic ram that actuates the links below the upper periphery of the traction wheel. It will be appreciated, therefore, that the lifting mechanism that I contribute will utilize merely a space that is normally present in trucks of the particular class, and will account for no part of the length of the truck.

I shall now describe in detail the construction of my novel hydraulic ram 32. Referring to Fig. 2, the cylinder 33 is closed at one end by a plate 63 welded thereto, and has its other end threaded for receiving a packing assembly 64. The cylinder 33 is formed near its outer end with a port 66 for connecting the cylinder to a source of fluid pressure P. The source of pressure P may be a part of a conventional type of hydraulic system, as shown diagrammatically in Fig. 2, with a check valve CV normally preventing an exhaust offluid from port 66, and a bypassing valve V whereby exhaust can be effected. Cylinder 33 has near its inner end a bottom port 67 that I utilize as a reservoir connection for the hydraulic system, as will be.

described, and also an upper port 68 that will be utilized when replenishing the supply of hydraulic fluid in the hydraulic system. This port 68 is normally closed by a plug 69, and is accessible through an opening 71, Figs. 4 and 5 in the floor 72 of the liftinghead 12.

I mount the cylinder 33 on the lifting head 12 through a pivot shaft 73 that extends through the cylinder near its closed end 63. As a bearing for this pivot shaft 73, I utilize a transverse sleeve 74, well shown in Figs. 2 and 3. That sleeve 74 is sealed by welding in openings in opposed sides of cylinder 33, as shown at 74a in Fig. 3, so that hydraulic fluid cannot leak from the cylinder 33 around pivot shaft 73. It will be appreciated that by that construction I contribute an extremely satisfactory pivot bearing that enables cylinder 33 to be arranged very close to the front of the truck.

For mounting the pivot shaft 73 on the lifting head 12, I show in Fig. 6, a pair of brackets 76 extending rearwardlyfrom the front of the lifting head at opposed sides of cylinder 33. The pivot shaft 73 is supported in openings inbracket 76 through end portions 77, 78 that are formed in the same axis, but I prefer, as seen in Fig. 7, to make eccentric the medial part 79 that coacts with the ram sleeve 74. Thus, by rotating the pivot shaft 73 relatively to bracket 76, I can adjust the position of the ram cylinder 33, The endportion 78 of the shaft 73 has a slot 82 for rotating the shaft, andthe opposed end 77 has a threaded portion 81 with a nut. 83, Fig. 6, for securing the shaft in a fixed position. If desired, the pins 49, which join the upper links 48 tothe lifting head 12, may have a similar eccentric construction for adjusting the position of said upper link.

Referring again to Fig. 2, the piston 34 in cylinder 33 has a head 86 that is threadedon one end of a hollow rod 87, with a set screw 88for the head 86. To prevent a movement of hydraulic fluidpast the head 86, the piston has preferably an annular packing 89 and an O-ring 91, said packing andO-ring beingheld in place by a circular plate 92 anda ring 93. The opposed end ofthe piston rod linkage 36., The packing assembly 64 will, of-course, proventthehydraulic. fluid from flowing outwardly around the pi ston rod 87. Th de ailsof this, assembly are.

not important to an understanding of my invention, but I do prefer to utilize in that assembly an annular nut 102, with inner threads for a gland 103 that retains a spring pressed packing 104.

I form that end of the piston rod 87 that is within the cylinder 33 with an axial bore 96 that extends for a substantial part of the length of the rod. In the bore 96 I utilize a coil spring 94 that presses at one end against the bottom of the bore. The opposed end of spring 94 presses against a spring guide 97 having a rod portion 98 extending within the spring. Spring guide 97 presses in turn against the transverse pivot sleeve 74 in cylinder 33, with a lug 100 on the guide 97 engaged in a dwell 99 to hold the guide aligned relatively to the'sleeve 74, all as shown in Fig. 2. Thereby the pressure of the spring 94 can act to extend the piston 34 relatively to cylinder 33.

To appreciate fully this action of spring 94, it should be observed that, when the parts are in the position shown in Fig. 2, piston 34 has been moved to its extreme inward position by the fluid pressure which has been applied to the left hand end of piston head 86 through the port 66 in cylinder 33. Therefore, the elevating platform 24 has been raised against the force of the spring 94. If we assume now that the piston 34 is relieved from fluid pressure to effect lowering of the platform 24, the the spring 94 will cause the piston 34 to extend relatively to the cylinder 33, moving away from the position shown in Fig. 2. Thereby the hydraulic ram 32 will act positively to move the load platform 24 to lowered position, and will promptly effect that movement even when no load is present on the platform. This I accomplish through the ram, and without requiring particular springs on the truck.

I shall now explain in detail, while referring to Fig. 2, those features that enable me to utilize the ram 32 as a reservoir for the hydraulic fluid. We will recall first that I so apply the fluid pressure to ram 32 as to move piston 34 in an inward direction in the cylinder 33. In other words, I apply the fluid pressure to cylinder 33 in the space around the piston rod 87, that space being at the left of piston head 86 as viewed in Fig. 2. Cylinder 33 has a further space 101 at the opposed right-hand end of piston head 86, that being the low pressure end of the piston head. Since rod 87 does not extend in that space 101, it will be seen that head 86 when moving in the cylinder will effect a somewhat greater displacement in space 101 than in the space in which the fluid pressure acts. It is important to realize further that the space 101 will still be of a very considerable size when the ram piston 34 is in the fully retracted position shown in Fig. 2. Therefore, it will be seen that the space 101 is well adapted not only to accept a quantity of fluid as that quantity is displaced at the pressure end of piston head 86, but in addition to hold a very substantial quantity of reserve fluid. Merely by placing the space 101 in communication with the hydraulic system through the port 67, the ram 32 can very effectively act as a reservoir for the system. Thus, through my novel ram construction, I obviate the need for a separate fluid reservoir and I do not require space for such a reservoir onthe truck.

I believe it will now be understood that I have contributed lifting means that are extremely novel and that have very considerable advantages over the lifting means utilized inthe prior trucks of the particular class. Through my invention, I am able to arrange the lifting ram, together with the lifting linkage, in an extremely small space on the truck, with the ram and linkage accounting for no part of the length of the truck. Moreover, I enable the ram to act positively to lower the elevating platform, and I do not require a separate spring for that purpose. My exceedingly novel ram also functions as a reservoir for the hydraulic fluid, thus eliminating the need for a separate reservoir on the truck. All of these things I accomplish through structure that is rather simple and easy to maintain. I believe, therefore, that d the merits of my invention will be fully appreciated by those skilled in the art.

I now claim: 1. In a truck of the class described, a lifting head, an elevating platform mounted for vertical movement relatively to said lifting head, a hydraulic ram comprising a piston and cylinder, means whereby the movement of the.

piston from a position outwardly of the cylinder of said ram to a position inwardly of the cylinder of said ram effects the lifting of the elevating platform relatively to said lifting head, a spring acting at all times between said ram cylinder and piston yieldingly to project said piston outwardly of said ram for pressing said elevating platform to a lowered position relatively to said lifting head, said cylinder having a space therein between the end of the piston when the piston is fully within the ram cylinder and the end of the ram cylinder towards which said piston is moved, and said space being at the low pressure side of the piston and forming a reservoir for said ram.

2. In a truck of the class described, a lifting head, an elevating platform mounted for vertical movement relatively to said lifting head, a hydraulic ram comprising a piston and cylinder, means whereby the movement of the piston from a position outward of the cylinder of said ram to a position inwardly of the cylinder of said ram effects the lifting of the elevating platform relatively to said lifting head, a fluid chamber in said cylinder in which fluid is moved by the end of the piston inward of said ram as said ram lifts the elevating platform, said chamber being at the low pressure side of the piston and forming a reservoir for said ram, and a spring in said ram cylinder acting at all times yieldingly to project said piston outwardly of said ram for moving said elevating platform to a lowered position relatively to said lifting head.

3. In a truck of the class'described, a lifting head, an elevating platform mounted for vertical movement relatively to said lifting head, a hydraulic ram comprising a piston and cylinder, means whereby the movement of the piston from a position outwardly of the cylinder of said rm to a position inwardly of the cylinder of said ram effects the lifting of the elevating platform relatively to said lifting head, a spring acting at all times between said ram cylinder and piston yieldingly to project said piston outwardly of said ram and thereby yieldingly pressing said elevating platform to a lowered piston relatively to said lifting head, said cylinder having a space therein between the end of the piston when the piston is fully within the ram cylinder and the end of the ram cylinder towards which said piston is moved, said space being at the low pressure side of the piston and forming a reservoir for said ram, a sleeve passing entirely through said space in said cylinder transversely of the axis of said cylinder, and a pivot shaft in said sleeve pivotally sup- I porting the cylinder on said lifting head.

4. In a truck of the class described, a lifting head, an elevating platform mounted for vertical movement relatively to said lifting head, a hydraulic ram comprising a piston and cylinder, means whereby the movement of the piston from a position outwardly of the cylinder of said ram to a position inwardly of the cylinder of said ram effects the lifting of the elevating platform relatively to said lifting head, a spring in said ram cylinder acting at all times yieldingly to project said piston outwardly of said ram for pressing said elevating platform to a lowered position relatively to said lifting head, said cylinder having a space therein between the end of the piston when the piston is fully within the ram cylinder and the end of the ram cylinder towards which said piston is moved, said space being at the low pressure side of the piston and forming a reservoir for said ram, a sleeve passing entirely through said space in said cylinder transversely of the axis of said cylinder, a pivot shaft in said sleeve pivotally supporting the cylinder on said lifting head, the spring lying within a central bore in said piston to press thereagainst: at one end, and, the opposed end, of said spring bearing against said sleeve.

5. In a truck of the class described, a lifting head, an elevating platform mounted for-vertieal movement: relatively to saidilifting head; a, hydraulic ram comprising a piston and cylinder, means whereby the movement of the piston from a position outwardly of the cylinder of said. ram;t.o,. a position inwardly ofthe cylinder of said ram, efiectsthe lifting of the elevatingplatfornl relatively to.

said lifting head, said cylinder having a space therein between the end of the piston when the piston is fully within the ram cylinder and the end ofthe ram cylinder towards which said piston is moved, said space being at the low pressure side of the piston and forming a reservoir for said ram, a pivot shaft for pivotally supporting the cylinder on said lifting head, and bearing means for said pivot shaft extending into the reservoir space and sealed relatively to the cylinder to prevent the escape of fiuid from said space.

6. In a truck of the class described, a lifting head, an elevating platform mounted for vertical movement relatively to said lifting head, a hydraulic ram comprising a piston and cylinder, means whereby the movement of the piston from a position outwardly of the cylinder of said ram to a position inwardly of the cylinder of said ram effects the lifting of the elevating platform relatively to said lifting head, a spring in said ramcylinder acting at all tirnes yieldingly to project said piston outwardly of said ram whereby to press said elevating platform to a lowered position relatively to said lifting head, said cylinder having a space therein between the end of the piston when the piston is fully within the ram cylinder and the end of the ram cylinder towards which said piston is moved, said space being at the low pressure side of the piston and forming a reservoir for said ram, a sleeve passing entirely through said space in said cylinder transversely of the axis of said cylinder, a pivot shaft insaid sleeve pivotally supporting the cylinder on said lifting head, the spring lying within a central bore in said piston to press thereagainst at one end, and a guide member for the opposed end of said spring bearing against a dwell in said sleeve.

7. In a truck of the class described, a lifting head, an elevating platform rearwardly of said lifting head, a battery on the lifting head in juxtaposed relation to the platform, a wheel supporting the forward end of said lifting head, said lifting head formed with a space extending from the rear end thereof forwardly below the battery and the top of said wheel, upper and lower parallel links, pivot means supporting the upper and lower links in close relation to one another and entirely within said space with each link pivoted at its opposed ends to said lifting head and elevating platform, said links supporting the rear end of said lifting head and the forward end of said elevating platform relatively to one another, a ram having a piston and cylinder, pivots on said piston and cylinder supporting the ram in a part of said space that is alignedin a horizontal direction relatively to said upper and lower links, means through which one of the ram pivots acts when said piston moves inwardly of said cylin der to swing the forward end of said elevating platform upwardly on said links to an elevated position, and a, spring, acting. between the ram cylinder. and piston. yield-i inglyvto press the piston outwardly Ofrthfi; cylinder f9 moving the elevating platform on said links ,to a, lowered position. relatively to the. lifting head.

8. In a lift truck. of the class described, an elevating platform, a lifting head arranged with its rear end closely.

juxtaposed tosaid elevating platform, a lower portion of said lifting head formed with a space extending forwardly therein from the rear end of said head, parallel links supported in positions one above another within said space,

means pivoting forward and rearward ends of each of to lift the elevating platform relatively to the lifting head.

on said links when the ram piston moves inwardly in the cylinder, and a spring pressing the ram piston in a direction outwardly of the cylinder for moving the elevating platform on said links to a lowered position relatively to the lifting head.

9. In a lift truck of the class described, an elevating platform, a lifting head arranged forwardly of said elevating platform, with the rear end of said lifting head closely juxtaposed to the platform, said lifting head having intermediate its length an upwardly extending wall, a battery compartment on said lifting head between the rear end of the lifting head and said wall, a ground engaging steering and traction wheel forwardly of the battery compartment on the lifting head, said lifting head having a space extending from the rear end of said head forwardly, and between the battery compartment and the ground and at one side of the steering and traction wheel, parallel links positioned one above another in a portion of said space extending between the rear end of the lifting head and a point that is vertically aligned with said upwardly extending wall, pivots mounting forward and rearward ends of each of said parallel links to rotate on said lifting head and elevating platform respectively, a ram having a cylinder and a piston, said piston being responsive to an application of fluid pressure to move inwardly of the cylinder, pivots on said piston and cylinder supporting said ram on the lifting head in position forwardly of the parallel links in said space and at one side of said wheel, and means through which one of said ram pivots acts when the piston moves inwardly of the cylinder to rotate the links in a direction on their pivots to lift the elevating platform relatively to the lifting head.

References Cited in the file of this patent UNITED STATES PATENTS 1,844,124 Jordan Feb. 9, 1932 2,090,768 Thomas Aug. 24, 1937 2,215,546 Dick Sept. 24, 1940 2,643,894 Schroeder June 30, 1953 2,686,036 Quayle Aug. 10, 1954 

